An Overall Plan for Sustainable Living 39The pressure of rapid population growth and wide-
spread poverty also harms the world’s forests. In many devel-
oping countries, forests have traditionally served as a “safety
valve” for the poor, who, by consuming small tracts of forest
on a one-time basis and moving on, find a source of food,
shelter, and clothing. But now the numbers of people in de-
veloping countries are too great for their forests to support.
Tropical rain forests—biologically the world’s rich-
est terrestrial areas—have been reduced to less than half
their original area. Methods of forest clearing that were
suitable when population levels were lower and forests
had time to recover from temporary disturbances simply
do not work any longer. Forests, if managed carefully, can
be a renewable resource. However, unsustainable use of
forest resources occurs when more trees are harvested
than are replaced, or when areas are replanted with low-
biodiversity commercial tree plantations.Loss of Biodiversity We have a
clear interest in protecting Earth’s
biological diversity and managing
it sustainably because we obtain
from living organisms all our food, most medicines, many
building and clothing materials, biomass for energy, and
numerous other products. In addition, organisms and the
natural environment provide an array of ecosystem services
without which we would not survive. These services include
the protection of watersheds and soils, the development of
fertile agricultural lands, the determination of both local cli-
mate and global climate, and the maintenance of habitats
for animals and plants.
Over the next few decades, we can expect human
activities to cause the rate of extinction to increase to
perhaps hundreds of species a day. How big a loss is this?
Unfortunately, we still have limited knowledge about
the world’s biological diversity. An estimated five-sixths
of all species have not yet been scientifically described.
Some 80 percent of the species of plants, animals, fungi,
and microorganisms on which we depend are found in
developing countries. How will these relatively poor coun-
tries sustainably manage and conserve these precious re-
sources? Biological diversity is an intrinsically local problem,
and each nation must address it for the sake of its own peo-
ple’s future, as well as for the world at large. Like most other
challenges of sustainable development, biological diversity
can be addressed adequately only if we provide interna-
tional assistance where needed, including help in training
scientists and engineers from developing countries.emphasize family planning measures, we simply will not
achieve population stability.
To stay within Earth’s carrying capacity, we must
reach and sustain a stable population and reduce excessive
consumption. These goals must be coupled with educa-
tional programs everywhere, so that people understand
that Earth’s carrying capacity is not
unlimited. There is no hope for
a peaceful world without overall
population stability, and there is no
hope for regional economic sustain-
ability without regional population
stability.
Recommendation 2:
Protect and Restore Earth’s Resources
To build a sustainable society, we must preserve the natural
systems that support us. The conservation of nonrenewable
resources, such as oil and minerals, is obvious, although
discoveries of new supplies of nonrenewable resources
sometimes give the illusion that they are inexhaustible. Re-
newable resources such as forests, biodiversity, soils, fresh
water, and fisheries must be used in ways that ensure their
long-term productivity. Their capacity for renewal must be
understood and respected. However, renewable resources
have been badly damaged over the past 200 years. Until en-
vironmental sustainability becomes a part of economic cal-
culations, susceptible natural resources will continue to be
consumed unsustainably, driven by short-term economics.
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iÊ 7À`½ÃÊ ÀiÃÌÃÊMany of the world’s forests
are being cut, burned, or seriously altered at a fright-
ening rate. In many parts of the developed world, old-
growth forests are rare and becoming more so. Much of
England’s forests were cut down centuries ago to build
ships and produce charcoal for fuel. As North America
was colonized, forests were first harvested along the
eastern seaboard. With expansion of the United States
and Canada, forests on the west coast were exploited for
construction, paper making, and fuel.
More recently, deforestation in developing countries,
has contributed to climate change and degradation of
soils. Tropical forests are particularly threatened by over-
exploitation. Many products—hardwoods; foods such as
beef, bananas, coffee, and tea; and medicines—come to
the industrialized world from the tropics. As trees are de-
stroyed, only a small fraction of them are replanted.
carrying capacity
The maximum
population that can
be sustained by a
given environment
or by the world as a
whole.biological
diversity The
number and variety of
Earth’s organisms.